Thanks for taking the time to write that how-to article. Unfortunately I cannot approve it because it describes an approach that the Core Team isn't comfortable recommending to concrete5 users.

While changing the config value will indeed tell the site to use the "Simple" permissions model, this doesn't guarantee that everything will work exactly as before. And while it may seem to work on one site, there's no way of guaranteeing that it will work on all sites, or even most sites. It is simply not in line with best practices. Let me try to elaborate:

Advanced permissions adds data to your database, and simply resetting a configuration value unfortunately doesn't clean up all that other stuff. Doing so manually would require a lot of work, which is why we warn that enabling Advanced Permissions cannot be un-done.

The best approach, if you're unsure about enabling Advanced Permissions, is to make a backup of your site's database before pressing the button (as JohntheFish mentioned) and restore it later, if needed. That's really the only way to safely avoid the possibility of frustrating and obscure edge cases. Backing up a database only takes a few seconds, but doing so can save many hours of work.

Of course if you're having fun in a development environment, you're welcome to experiment. But if your site is live and you want to ensure a healthy working relationship with your client, please know that Advanced Permissions was not intended to be turned "off" after being activated. If you do so, you're in uncharted territory!

Hope that helps explain where we're coming from. Best of luck to you and thanks again for contributing a how-to article!